If you’re planning to be here four billion years from now you’ll see an amazing slow-motion sky show when two galaxies collide — Andromeda and our own Milky Way.

What will the sky look like when that happens? (very amazing!)

Will it be dangerous for Earth?  (probably not)

How many years before this happens?

Billions and billions.

(video posted in June 2012 by SpaceRip on YouTube)

video by Sriram Murali on Vimeo

18 November 2016

Have you ever seen the Milky Way?

That question would have been absurd 200 years ago because billions of stars were visible on every clear night.

But now with the prevalence of artificial outdoor light most of us cannot see the Milky Way and many children don’t know what it is.

Because of this, some ancient stories don’t make sense.  In Genesis Abraham worried that he had no heir but God reassured him, “Look up into the sky and count the stars if you can. So many shall your descendants be.”   Today we look at the sky and count 50 stars, not realizing that Abraham saw millions and was overwhelmed.

So what are we missing?  Sriram Murali traveled in California recording time-lapse video of the night sky in places with high light pollution (San Jose) and almost no artificial light (Death Valley).

His video let’s us see the sky as our ancestors did.

Watch the stars come out.

(video by Sriram Murali)

29 October 2016

In the olden days the first killing frost in Pittsburgh usually occurred by Halloween and we had to wear winter coats over our costumes while trick-or-treating.  … I always hated to cover my costume.

This year has been very warm, even hot.  Only ten days ago it felt like August and today the temperature is 5-10 degrees above normal.  When will we experience the first killing frost?

Some of you already have.  If you live east or north of Pittsburgh the growing season is shorter (bluer), as shown on the USDA Plant Hardiness Map below.  Bradford, Pennsylvania is three growing zones colder than Pittsburgh and the Monongahela and Ohio Valleys.  I’ll bet they’ve had a killing frost.

Here in Pittsburgh the weather forecast says we won’t dip near freezing for the next several days.  Today it’ll be 10 degrees above normal.

When do you think we’ll have our first killing frost?

(photo of frosty leaves by Dianne Machesney, excerpt from USDA Plant Hardiness map at USDA.gov)

The days are getting longer.  Really.

Though daylight is decreasing as we head into winter, the length of an Earth day is increasing overall. That’s because Earth’s rotation is slowing down due to tidal forces between Earth and moon, post-glacial rebound, and sea level rise.

The effect is too tiny to see.  It takes 100 years for the day to gain 1.4 milliseconds.  To put that in perspective, a day was 23 hours long for the dinosaurs and is close to 24 hours now.

The only way we can measure Earth’s rotation is by using an array of instruments stationed around the globe (VLBI) that precisely record their first sighting of certain quasars. We then crunch the data to arrive at the length of a day and add a second to our atomic clocks when necessary.

Want to learn how we measure a day?  See the video about quasars at this NASA link.

(*) Quasars emit radio waves so they aren’t actually seen, they’re heard.

(animation of earth’s rotation from Wikimedia Commons. Click on the image to see the original)

Something really big exploded 5,000 to 10,000 years ago and this is what’s left.

The Cyngus Loop or Veil Nebula is the dust and gas left over when a supernova exploded in the area of the Cygnus constellation.  The explosion was so bright that people could see it naked eye.

But they didn’t write about it.  The first written language was invented by the Sumerians 5,200 years ago, probably too late for anyone to mention a temporary bright spot in the sky.

Nowadays the remnants are too dim to see without a telescope and some sections such as the Witch’s Broom have been named separately.

The entire Veil, above, isn’t visible except in the ultraviolet range.  If we could see it we’d be impressed.  It’s six times the size of the full moon.

p.s. Many birds can see light in the ultraviolet range, so this is probably what the Veil looks like to them.

(ultraviolet image of the Cygnus Loop Nebula by NASA/JPL-CalTech via Wikimedia Commons. Click on the image to see the original)

1 October 2016

If it’s clear tonight in Pittsburgh you’ll be able to see the International Space Station (ISS) traverse the sky for six minutes.

At 7:41pm the ISS will appear in the southwest and pass directly overhead on its way northeast at 17,150 miles per hour.  At five miles per second it doesn’t take long to disappear.  Read more here in the Post-Gazette on what and where to look for it.

You don’t have to be in southwestern Pennsylvania to see it.  NASA’s Spot The Station website predicts ISS’s appearances around the world.

Armed with this information you can impress your friends.  Casually looking at the night sky you can say, “Look over there.  In half a minute the International Space Station will appear on the horizon and pass directly overhead.”

A fast-moving shiny thing in the sky.

(photo of the International Space Station as seen from the Space Shuttle Atlantis, 19 July 2011.  Click on the image to see the original)

p.s. Unless they’ve already fixed it, I believe there’s a typo in the Post-Gazette’s 2nd paragraph which says “Monday” but probably means Saturday.